A Blog by Jonathan Low

 

Feb 20, 2021

Study Shows 1 Dose of Pfizer Vax Effective, Can Be Stored In Normal Freezers

This could speed global inoculation against the virus. JL 

Denise Chow reports in NBC:

Scientists found that the vaccine was 85% effective at preventing symptomatic Covid-19 within 15 to 28 days after the shot was administered. The study also found a 75% reduction in both symptomatic and asymptomatic infections after just the first shot. "Early reductions of Covid-19 rates provide support of delaying the second dose in countries facing vaccine shortages and scarce resources, so as to allow higher population coverage with a single dose." (And) it provides reassurance that (given) delays for weather or supply chain, individuals who have received the one dose achieve a good level of protection.

The Covid-19 vaccine developed by Pfizer and BioNTech produces a robust immune response after just one dose, according to a new Israeli study of vaccinated health care workers at the country's largest hospital.

The research, published Thursday in the medical journal The Lancet, followed 7,214 staff members at Israel's Sheba Medical Center, a government-owned facility, who received their first dose of the Pfizer-BioNTech vaccination between Dec. 19 and Jan. 24. Scientists from the medical center found that the vaccine was 85 percent effective at preventing symptomatic Covid-19 within 15 to 28 days after the shot was administered.

Experts cautioned that more research is needed before broad conclusions can be drawn, but the results do provide some evidence that robust immunity is generated after one dose and that the second dose could be delayed beyond the three weeks prescribed by Pfizer in order to ease distribution and supply constraints.

The timing of the second dose has been the subject of much recent debate, with some countries such as the United Kingdom opting to delay it as a way to speed up the country's rate of immunization. In the United States, where the vaccine rollout has been bumpy and winter storms over the past week have hampered some states' ability to administer shots, similar questions have emerged.

Dr. Jonathan Temte, a vaccine expert at the University of Wisconsin School of Medicine and Public Health who was not involved with the Israeli study, said any sweeping changes to immunization recommendations would require more data, but that the results of the new study are encouraging.

"It does provide reassurance that delays for whatever reason, be it the weather or problems in the supply chain — it provides some comfort knowing that those individuals who have received the one dose do achieve a good level of protection," he said.

Official guidance from the Food and Drug Administration and Pfizer-BioNTech state that the two doses should be administered 21 days apart based on the results of clinical trials. For the Moderna vaccine, the only other vaccine currently authorized for use in the U.S., the prescribed interval between the two shots is 28 days.

But vaccine supplies are limited and different strains of the virus are circulating around the country, putting pressure on states to quickly vaccinate as many people as possible. Some have questioned whether there is flexibility in the timing of the second dose.

Last month, the Centers for Disease Control and Prevention updated its guidance to say that the second shot should be administered within the prescribed time frames where possible, but that the second dose of the Moderna and the Pfizer-BioNTech vaccines could be delayed up to six weeks, if necessary.

Pfizer has said it has not yet studied changes to the timing between doses, and the drugmaker has maintained that any deviations to the dosing schedule is up to health authorities.

In the new Israeli study, researchers reported 170 Covid-19 infections among health care workers at the Sheba Medical Center between Dec. 19 and Jan. 24. Of those, 78 people tested positive after receiving the first dose and three individuals tested positive after receiving the second dose. Since the vaccines are not 100 percent effective, it is expected that a small number of people could contract the virus even after being fully vaccinated.

The study also found a 75 percent reduction in both symptomatic and asymptomatic infections after just the first shot. The scientists said these reductions suggest that one dose provides a robust enough immune response to justify delaying the second shot.

"Early reductions of Covid-19 rates provide support of delaying the second dose in countries facing vaccine shortages and scarce resources, so as to allow higher population coverage with a single dose," the researchers wrote in the study.

They acknowledged, though, that testing limitations may have resulted in undercounted asymptomatic cases and that follow-up research is needed to assess the long-term effectiveness of a single dose.

The findings provide some of the first real-world data on the effectiveness of a single vaccine dose. Israel's vaccination program has far outpaced any other country, and more than 30 percent of the country's 9 million residents have already received both doses.

Temte said that while early results from Israel's vaccine program are positive, there are still too many unknowns about a single dose's efficacy beyond three to six weeks.

"Until such time that there are good clinical trials that show that a single dose provides an equivalent level of protection, I don't know that we should abandon our approach or create new policies," he said.

It's also not clear how one dose will perform against different coronavirus strains that are becoming more widespread, including separate strains that were first reported in the U.K., South Africa and Brazil.

"We're running into uncharted territory," said Deepta Bhattacharya, an associate professor of immunobiology at the University of Arizona, who was not involved with the study. "The uncertain issue is how long that protection is going to last against the current variants, as well as some of the ones that might get selected for if you wait too long."

Bhattacharya said delaying the second dose up to six weeks, in line with the CDC's guidance, seems reasonable. But beyond that, it may be too soon to tell, which means health officials may be faced with tricky decisions.

"We're stretching the limits of what we're able to see," he said. "We’re sort of at a point now where we have to make decisions based on imperfect evidence."

2 comments:

Jimmy said...

选择专业其实因人而异。很难给所有的人一个标准答案。必须根据每个人的不一样的情况给出完全不同的建议。这是几千人的问题,不是北美数学代写 的问题。通常,只有一个standard答案。根据近年来的个人经验,无论您们选择什么专业,这个专业都会有优点和缺点。例如,科技是祸福难测,专业也是如此。在这种情况下,我们需要分析数学有什么优点,有什么缺点。只有这样,我们才能够根据自身的情况来具体分析,然后决定最终是否选择数学的专业。

Emma Watson said...

Sadly, objections list underhanded cutoff points we can't regard. Learn about our advancement code strategy. Best Discount code site Now the Best Holiday Rentals in Malaga. Holiday Accommodation on the Blue Sea Holidays This is a very ecstatic time for them. During these events. A total london travel guide for visiting London from the experts at Condé Nast Traveler. london travel guide Add class to your look with this infamous worldwide clothing brand that is known to be up-scale with striking quality. Emporio Armani Whether it's California surfing, Maine tide pooling, or Florida swimming that stimulates the explorer, Beach Vacations a sensible sea side move away is holding on. Ocean side Vacations Grab your markdown code now and put away to 70% at Fashion Discount code Save up to half with these continuous coupons The latest coupon codes at voucher pro. Beauty Discount code Set aside to 25% OFF with these nonstop shopping express coupon code Shopping Discount Code We have got a lot of vouchers, discounts, and promotions ... food to get special discount Latest Discount Code


Post a Comment